'Tickling' The Brain Can Boost Immunity, Says Study

Artificially stimulating the brain's feel-good centre boosts immunity in mice in a way that could help explain the power of placebos, a study reported Monday.

"Our findings indicate that activation of areas of the brain associated with positive expectations can affect how the body copes with diseases," said senior author Asya Rolls, an assistant professor at the Technion-Israel Institute of Technology's Faculty of Medicine.

The findings, reported in Nature Medicine, "might one day lead to the development of new drugs that utilise the brain's potential to cure," she said.

It has long been known that the human brain's reward system, which mediates pleasure, can be activated with a dummy pill devoid of any active ingredients — known as a placebo — if the person taking it thinks it's real medicine.

"But it was not clear whether this could impact physical well-being," Rolls told AFP.

Nor did scientists know — if, indeed, an immune response was strengthened — exactly how the signal travelled through the body.

Rolls and colleagues incubated immune cells from mice exposed to deadly E. coli bacteria after specific cells in the animals' reward centre had been stimulated.

These immune cells were at least twice as effective in killing bacteria than ordinary ones, they reported.

In a second test, the scientists vaccinated different mice with the same immune cells.

Thirty days later, the new set of rodents was likewise twice as likely to be able to fight off infection.

Food and sex

The immune-boosting information emanated from a part of the brain called the ventral tegmental area, home to a reward system powered by the mood-modifying chemical dopamine.

This area lights up in brain scans when a mouse — or a human — knows that a tasty meal, or a sexual encounter, is in the offing.

From there, the study found, the message is routed via the sympathetic nervous system, which is responsible for snap responses in a crisis situation, until it triggers the bacteria-fighting immune response.

Evolutionary pressures may play a key role in the observed association, the researchers speculated.

"Feeding and sex expose one to bacteria," explained Rolls said.

"It would give one an evolutionary advantage if — when the reward system is activated — immunity is also boosted."

The next step will be mice experiments to find molecules — potential drugs — that could reproduce this cause-and-effect.

"Maybe they could be used as new therapeutic targets," Rolls said.

The breakthrough was made possible thanks to a pair of new technologies, said the study's other lead author, Shai Shen-Orr, also from the Technion-Israel Institute of Technology.

One enables neurons to be switched on an off. The second gives scientists high-resolution profiles of hundreds of thousands of cells in the immune system.

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Stunning Brain Images Reveal Beauty Of Fragile Brain

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Just like the electrical wires in the national grid, the electrical connections between brain cells, as shown in this picture, have to be well insulated. If this insulation is lost, neurons lose their ability to communicate efficiently. This is what happens in several neurological diseases including multiple sclerosis (MS).

This colorful picture shows the wiring in a developing brain. Axons (red) are the cables that neurons use to transmit their information, often over relatively long distances and taking highly circuitous routes. The other colors represent different areas of the brain.

At first glance this may look like a spider’s web but this web measures just 1/20 of a millimeter. It is made up of two types of brain cells – astrocytes in green and a white oligodendrocyte. These cells were originally thought of as the support cells for neurons but it is now known they are essential for many brain functions.

This picture of neurons from a female brain highlights those that have switched off the X chromosome inherited from the mother (in green), and those that have silenced the X chromosome inherited from the father (in red). In cases where an altered gene on one of the X chromosomes causes autism or intellectual disability, only around a half of the cells will be affected. This helps to explain why these conditions are less common in women than in men.

This image shows differences between a typical brain (left) and autism (right). The different colors identify different areas of the brain.

These star-shaped cells, or “astrocytes,” were once thought to be simple support cells for neurons. Now we know that they are much more important than this--they also help to create and maintain an environment in the brain that is optimized for electrical and chemical communication.

Scientists can use mathematics to model brain circuitry, as shown in this picture. They use this approach to predict how brain communication is altered in neuropsychiatric disorders, such as anxiety and ADHD.

This is a detailed map of the brain wiring in a sleeping newborn baby (left) and an adult in their seventies (right), visualized using MRI.

Neurons talk to one another across a gap called the synaptic cleft, rather than being directly connected to one another. A trained eye can identify the wires that are transmitting messages and those that are receiving information in this picture.

Neurons have branched projections that extend from their cell body called dendrites which give the cells a tree-like appearance. It’s through these dendrites that neurons receive information from hundreds to thousands of other cells.

Our brains hold specialized neurons called grid cells that help us to keep track of where we are. This heat map shows the regions in space where an individual grid cell becomes active during exploration of a circular room.

This picture shows the egg or “oocyte” preparing the genes that will be passed on to its offspring, which are highlighted in red.

Images such as this one, which shows the spinal cord from a zebrafish repairing itself, are helping scientists to study biological mechanisms that could one day reveal treatments for people who are paralyzed due to spinal cord damage.

This picture shows the difference in brain signals from a typical brain (left) and from a brain affected by a condition similar to Fragile X Syndrome, the most common inherited form of autism (right).

This is a close-up image of a particular area of the brain called the hippocampus, named from the Greek word for “seahorse” because of its shape.

This image shows a series of MRI pictures from the brain of an individual with Fragile X Syndrome, the most common inherited form of autism.